restore categoryFields in the API

src/runtime/c/pgf/pgf.cxx

@@ -2047,6 +2047,38 @@ int pgf_has_linearization(PgfDB *db, PgfConcrRevision revision,
     return 0;
 }
 
+PGF_API
+PgfText **pgf_category_fields(PgfDB *db, PgfConcrRevision revision,
+                              PgfText *name, size_t *p_n_fields,
+                              PgfExn *err)
+{
+    PGF_API_BEGIN {
+        DB_scope scope(db, READER_SCOPE);
+
+        ref<PgfConcr> concr = PgfDB::revision2concr(revision);
+
+        ref<PgfConcrLincat> lincat =
+            namespace_lookup(concr->lincats, name);
+
+        if (lincat == 0) {
+			*p_n_fields = 0;
+			return NULL;
+		} else {
+			size_t n_fields = lincat->fields->len;
+			PgfText **fields = (PgfText **) malloc(sizeof(PgfText*)*n_fields);
+			if (fields == 0)
+				throw pgf_systemerror(ENOMEM);
+			for (size_t i = 0; i < n_fields; i++) {
+				fields[i] = textdup(lincat->fields->data[i]);
+			}
+			*p_n_fields = n_fields;
+			return fields;
+		}
+    } PGF_API_END
+
+    return NULL;
+}
+
 PGF_API
 PgfText *pgf_linearize(PgfDB *db, PgfConcrRevision revision,
                        PgfExpr expr, PgfPrintContext *ctxt,

src/runtime/c/pgf/pgf.h

@@ -590,6 +590,11 @@ PGF_API_DECL
 int pgf_has_linearization(PgfDB *db, PgfConcrRevision revision,
                           PgfText *name, PgfExn *err);
 
+PGF_API
+PgfText **pgf_category_fields(PgfDB *db, PgfConcrRevision revision,
+                              PgfText *name, size_t *p_n_fields,
+                              PgfExn *err);
+
 #ifdef __cplusplus
 struct PgfLinearizationOutputIface
 {

src/runtime/haskell/PGF2.hsc

@@ -74,7 +74,7 @@ module PGF2 (-- * PGF
              linearize, linearizeAll, tabularLinearize, tabularLinearizeAll,
              FId, BracketedString(..), showBracketedString, flattenBracketedString,
              bracketedLinearize, bracketedLinearizeAll,
-             hasLinearization,
+             hasLinearization, categoryFields,
              printName, alignWords, gizaAlignment,
 
              -- ** Parsing
@@ -613,6 +613,27 @@ hasLinearization c name =
     c_res <- withPgfExn "hasLinearization" (pgf_has_linearization (c_db c) c_revision c_name)
     return (c_res /= 0)
 
+categoryFields :: Concr -> Cat -> Maybe [String]
+categoryFields c cat =
+  unsafePerformIO $
+  withForeignPtr (c_revision c) $ \c_revision ->
+  withText cat $ \c_cat ->
+  alloca $ \p_n_fields ->
+  bracket (withPgfExn "categoryFields" (pgf_category_fields (c_db c) c_revision c_cat p_n_fields)) free $ \c_fields ->
+    if c_fields == nullPtr
+      then return Nothing
+      else do n_fields <- peek p_n_fields
+              fs <- peekFields n_fields c_fields
+              return (Just fs)
+  where
+    peekFields n_fields c_fields
+      | n_fields == 0 = return []
+      | otherwise     = do c_text <- peek c_fields
+                           f  <- peekText c_text
+                           free c_text
+                           fs <- peekFields (n_fields-1) (c_fields `plusPtr` (#size PgfText*))
+                           return (f:fs)
+
 -- | Linearizes an expression as a string in the language
 linearize :: Concr -> Expr -> String
 linearize c e =

src/runtime/haskell/PGF2/FFI.hsc

@@ -210,6 +210,8 @@ foreign import ccall pgf_drop_lin :: Ptr PgfDB -> Ptr Concr -> Ptr PgfText -> Pt
 
 foreign import ccall pgf_has_linearization :: Ptr PgfDB -> Ptr Concr -> Ptr PgfText -> Ptr PgfExn -> IO CInt
 
+foreign import ccall pgf_category_fields :: Ptr PgfDB -> Ptr Concr -> Ptr PgfText -> Ptr CSize -> Ptr PgfExn -> IO (Ptr (Ptr PgfText))
+
 foreign import ccall pgf_linearize :: Ptr PgfDB -> Ptr Concr -> StablePtr Expr -> Ptr PgfPrintContext -> Ptr PgfMarshaller -> Ptr PgfExn -> IO (Ptr PgfText)
 
 foreign import ccall pgf_linearize_all :: Ptr PgfDB -> Ptr Concr -> StablePtr Expr -> Ptr PgfPrintContext -> Ptr PgfMarshaller -> Ptr CSize -> Ptr PgfExn -> IO (Ptr (Ptr PgfText))

src/runtime/haskell/tests/linearization.hs

@@ -19,6 +19,8 @@ main = do
       ,TestCase (assertEqual "floatLit" "3.14" (linearize cnc (mkApp "floatLit" [mkFloat 3.14])))
       ,TestCase (assertEqual "stringLit" "abcd" (linearize cnc (mkApp "stringLit" [mkStr "abcd"])))
       ,TestCase (assertEqual "parse tree 2" graphviz_parse2 (graphvizParseTree cnc graphvizDefaults (mkApp "stringLit" [mkStr "abcd"])))
+      ,TestCase (assertEqual "categoryFields 1" (Just ["s"]) (categoryFields cnc "N"))
+      ,TestCase (assertEqual "categoryFields 2" Nothing (categoryFields cnc "NonExistingCat"))
       ]
 
 graphviz_parse1="graph {\n  node[shape=plaintext]\n\n  subgraph {\n    rank=same;\n    n1[label=\"c : S\"]\n  }\n\n  subgraph {\n    rank=same;\n    n2[label=\"s : N\"]\n  }\n  n1 -- n2\n\n  subgraph {\n    rank=same;\n    n3[label=\"_ : N\"]\n  }\n  n2 -- n3\n\n  subgraph {\n    rank=same;\n    edge[style=invis]\n    n100000[label=\"?1\"]\n    n100001[label=\"+\"]\n    n100002[label=\"1\"]\n    n100000 -- n100001 -- n100002\n  }\n  n3 -- n100000\n  n2 -- n100001\n  n2 -- n100002\n}"